2115 GMT: We're closing off our coverage for the night with news that Mousavi has called for the release of protesters arrested in the past days' rallies. That news comes via CNN, who also have more on the Iranian football team's green wrist bands.

One of the banners from the Iran-South Korea World Cup football qualifier: "Go to Hell Dictator".

1600 GMT: Al Jazeera English have obtained film of the rally from 7 Tir Square showing thousands of people, most silent, marching. The gathering is calm.

Thank goodness for these images because the Iranian Government is now trying to squeeze out any notion of legitimate protest. Press TV English is leading with the Foreign Ministry's denunciation of "irresponsible meddling" by Western governments. The "American card" is now being played: amongst those summoned by the Ministry to hear the Government's protests is the Swiss Minister, the representative of US interests, and the Intelligence Ministry is saying that opposition websites are funded by American and British companies.

1510 GMT: Reports indicate that the demonstration in 7 Tir Square is so large that people are having problems getting off the underground and buses into the square.

If true, this may be one of the largest gatherings to be "non-covered" by the media. International journalists are effectively shut away, and state-run Press TV English is not saying a word about the rally.

1315 GMT: Among the 100+ reportedly arrested on Tuesday: Saeed Hajjarian, former Tehran councillor and advisor to President Khatami, Mohammad Ali Abtahi, Vice President under Khatami, and Mohammad Tavassoli, first mayor of Tehran. Ibrahim Yazdi, head of the Freedom Movement of Iran, avoided arrest because he was not at home.

Opposition activist Saeed Leylaz, who gave interviews over weekend to American and British media, also arrested.

1303 GMT: Reports that today's opposition demonstration will converage on 7 Tir Square from two directions, one group coming from Tehran University via Enqelab Avenue and one coming from Vanak Square.

The Iran national football team initially wore, then removed, green wristbands in their World Cup qualifying match with South Korea.

1300 GMT: Have just returned from BBC; staff said they are almost "blind" in Iran because of restrictions. Many CNN reports now consist of a London staffer walking into a room of computers and pointing out what is on YouTube.

1130 GMT: I am off for a live interview with BBC World TV, airing about 1215 GMT.

Press TV English is now doing a balancing act, following news of the enquiry into the attacks on the Tehran University dormitories with a report on an Intelligence Ministry report to the Parliament, followed by their joint declaration urging "people to exercise restraint. No one should act in such a way as to play into the hands of the Western countries and Israel."

The Iranian Foreign Ministry has also criticised "irresponsible meddling....insulting to the Iranian's people intelligence" by Western countries.

0930 GMT: I am off for an interview with BBC News about the current US approach to Iran.

0920 GMT: Friday is shaping to be an important day in this crisis. As Dr Seyed Mohammad Marandi indicated in our discussion on Al Jazeera yesterday, Ayatollah Khamenei will lead Friday prayers, while Mousavi supporters are saying they will march to the site.

0830 GMT: We wondered earlier what former President Rafsanjani was doing (0600 GMT). Reports emerging that he is meeting with the Expediency Council, an Iranian body which officially resolves differences or conflicts between the Iranian Parliament and the Guardian Council and also advises the Supreme Leader.

Press TV English reports that the Minister of the Interior has ordered an enquiry into the security forces' raid on Tehran University dormitories earlier this week.

0800 GMT: The official line inside Iran seems clear: Press TV English has just devoted the first minutes of its hourly news to the Supreme Leader's call for calm and unity. CNN has been reduced to repeating its "social media" story while Al Jazeera's correspondent in Tehran is struggling with poor sound and poor visibility in his office.

Outside Iran, however, there are interesting turnings. From London, Nazanin Ansari, the diplomatic editor of Kayhan newspaper, is telling Al Jazeera, "What the Supreme Leader has done, he has actually cornered himself. Soon you will see the Leader against the population and the marchers. We hear the chants of, "Down with the Dictator! Down with the Dictator! It is not so much against Mr Ahmadinejad as it is turning against the Supreme Leader."

0700 GMT: A reply via Twitter to our question below about Obama's statements on Iran, "He is allowng it to remain Iranian fight. Not Iran v US. If it became about US, [Iranian] government would crack hard on protesters. Government could say this is about US interference & really go after protesters. Not now. This is Iran people wanting change."

0630 GMT: We're still working through last night's somewhat curious statement by President Obama to CNBC, "I think it’s important to understand that either way we are going to be dealing with a regime in Iran that is hostile to the US." On the surface, it appears that he is both 1) maintaining the line that Washington will "engage" with Ahmadinejad if he remains in power; 2) damping down expectations of sudden movement in US-Iran relations if Mir Hossein Mousavi does becomes President.

Fair enough from a power politics standpoint. But, given the spin about US support for free expression and fair politics, what message does Obama's statement send to those demonstrating for a challenge to last Friday's vote? (My colleague Steve Hewitt has noted that yesterday morning, British Foreign Minister David Miliband sent out a similar message of "Mousavi is not a reformist" on the BBC.)

We've posted the videos of Obama's interview with CNBC and his earlier statement on Iran at his press conference with South Korea's President.

That social media, while invaluable, can only offer a partial and uncertain picture. There are reports of more raids by police and paramilitary Basiji on university dormitories overnight --- we have video of the aftermath of one raid at Isfahan. Indications are that protests against President Ahmadinejad's re-election will take place in Tehran around 4 or 5 p.m. local time (1130-1230 GMT).

Politically, the notable intervention last night was the call of the Supreme Leader, Ayatollah Khamenei, for calm and unity after his meeting with representatives of the four Presidential campaigns. The statement appears to be an attempt to get political breathing space, rather than a move towards a settlement, as the Guardian Council purportedly reviews part of last Friday's vote. The presence of opposition campaigns at the meeting indicates a willingness to support the Supreme Leader's call for non-violence; what will be more interesting will be their response (and the response of their supporters) to the implied plea for time to let the Guardian Council do its work.

(It is also notable, for us, that there has been no indication of former President Rafsanjani's political moves after his visit to Qom earlier this week to seek the support of senior clerics and the Assembly of Experts. President Ahmadinejad, meanwhile, is effectively on the sidelines while he is out of the country.)